Apparently gsettings needs some variables to be set. Because CRON uses only a very restricted set of environment variables you must set them before your script. Use the following code in your CRON line.
30 */2 * * * DISPLAY=:0 GSETTINGS_BACKEND=dconf /your/path/your-script.sh
In the example the job is set to run every 2 hours on the 30th minute. I've tried to insert the variables into the script, for a cleaner line, with no result, if someone find a way to do that, let us know.
Stumbled with these settings in ArchLinux forums.
The above solution no longer works with Vivid.
The best way to get this to work is indeed to find DBUS_SESSION_BUS_ADDRESS variable, in the following script I'm using a for loop to do the job because using pidof of a specific application like gnome-session doesn't always work for me and the newers applications have a different DBUS ADDRESS probably because, in my particular case, I'm starting some daemons on boot with my user name. To effectively change the wallpaper I'm using dconf but you can also use gsettings. So tweak the script to your use case.
#!/bin/bash -e
user=$(whoami)
fl=$(find /proc -maxdepth 2 -user $user -name environ -print -quit)
while [ -z $(grep -z DBUS_SESSION_BUS_ADDRESS "$fl" | cut -d= -f2- | tr -d '\000' ) ]
do
fl=$(find /proc -maxdepth 2 -user $user -name environ -newer "$fl" -print -quit)
done
export DBUS_SESSION_BUS_ADDRESS=$(grep -z DBUS_SESSION_BUS_ADDRESS "$fl" | cut -d= -f2-)
if [ $# -gt 0 ]
then
PICS_PATH=$1
else
PICS_PATH="/home/public/Pictures/Wallpaper/"
fi
IMG=$(find -L $PICS_PATH -name "*.jpg" -o -name "*.png" | shuf -n1)
#gsettings set org.gnome.desktop.background picture-uri "file://${IMG}"
dconf write "/org/gnome/desktop/background/picture-uri" "'file://${IMG}'"
echo -e "$(date): ${IMG}" >> /tmp/wallch.log
in crontab add the following line to change wallpaper every even hour
0 */2 * * * /path/to-above-script.sh /path/to-wallpapers/
Best Answer
Make a script as this example called
dailywallpaper.sh:The script usage is explained in the script's comments. You can set the script to run via
crontab.Crontab example entry:
The Startup Applications app is needed if you are not logged in at midnight. The startup app will make the change when you log in. You can find the Startup applications app in the Ubuntu Dash: (Ubuntu Dash ->
Startup Applications).The
crontabentry sets the background variable if you are logged in. TheStartup Applicationsapp sets the variable if you were not logged in at midnight when the cron ran.Using the two, the correct day's wallpaper will always show.